When producing an ingot cast, such as in an aluminum casting process, control of metal flow into the mold is an important factor. For example, at the extremes, excessive metal flow could cause a mold to overflow or otherwise exceed appropriate boundaries and damage other equipment, while inadequate flow could allow metal to cool and solidify before reaching boundaries of the mold and result in ingots having undesirable shapes or other negative characteristics.
Appropriate flow control can be challenging to maintain due to fluctuations that can occur in flow behavior even when other variables are steadily maintained and not changed. Take for example, a conduit that can be closed to different degrees by moving a tapered pin to be closer or farther from engagement with a similarly tapered opening of the conduit. Even if the pin is held at a constant position, flow rate out through the partially obstructed opening may vary according to a number of factors, such as an amount and weight of molten metal behind the pin in the mold, composition of the flowing metal, temperature, etc.
Often, such fluctuations are accounted for by automated algorithms that detect a metal level in the mold, compare the detected level to a target level (e.g., setpoint), and respond by altering a pin position (or other setting of some other flow control device) to address discrepancies between the detected and target levels. For example, the pin may be opened a small amount in response to determining that the detected level is slightly lower than the setpoint, opened a larger amount in response to a greater determined deficiency, and moved incrementally in a closing direction upon registering that the detected level is above the setpoint.
Although such algorithms can provide useful control for mitigating level deviation, flow control issues can still arise. For example, in operation of such algorithms, the actual metal level may “overshoot” or “undershoot” the setpoint by a significant amount when flow rate requirements change suddenly. Such overshoot or undershoot may negatively affect process control, cause the cast to abort (e.g., due to the detected level falling outside approved parameters), or otherwise negatively affect casting processes.